Safety and risk assessment frameworks for offshore CO2 storage

Offshore carbon capture and storage (CCS) is increasingly recognized as an important strategy for reducing large-scale greenhouse gas emissions. However, its deployment depends on demonstrating long-term operational safety, environmental protection, and regulatory confidence. This study reviews safety and risk assessment frameworks for offshore geological CO 2 storage and clarifies the conceptual distinction between safety as the desired operational condition and risk as the probability and consequence of adverse events. Key risk pathways include leakage through faults and wells, induced seismicity, brine displacement, operational hazards, and potential impacts on marine ecosystems. Evidence from major offshore CCS projects, including Sleipner and Snøhvit, is used to illustrate practical risk management experience. The review compares qualitative, semi-quantitative, and quantitative risk assessment methods and discusses how their application evolves across the CCS lifecycle, from early site screening to operation and post-closure stewardship. Integrated frameworks such as the U.S. Department of Energy’s National Risk Assessment Partnership (NRAP) and the International Energy Agency Greenhouse Gas R&D Programme (IEAGHG) are examined for their role in supporting probabilistic analysis and regulatory decision-making. The study also highlights monitoring technologies, modelling tools, and remaining challenges related to long-term stewardship, data availability, regulatory coordination, and stakeholder confidence.